1. Field of the Invention
This invention relates to, and has as its principal objects provision of, novel ultraviolet-absorbing agents containing organosilane ester groups useful to provide light-and scratch-resistant coatings, particularly for plastics, the novel coating solutions and coatings produced, and the coated articles, especially those made from polycarbonates, resulting from the coatings.
2. Description of the Prior Art
Many polymers, especially polycarbonates, are deficient in weatherability due to adverse effects of ultraviolet (UV) light, which causes yellowing and surface degradation and lack of abrasion resistance. Compatible coatings containing polysilicic acid as described in U.S. Pat. No. 3,429,845 have been found useful in increasing resistance to scratching but they may lack adhesion to some plastics, particularly on exposure. Incorporation of ultraviolet light absorbers has not been effective due to their loss by migration, volatilization and leaching during curing and/or exposure of the coating.
A polymeric ultraviolet absorber has been suggested in U.S. Pat. No. 3,340,231 and 3,341,493 wherein an epoxy monomer such as an unsaturated glycidyl ester is reacted with 2,4-dihydroxybenzophenone and its resulting monomer used in copolymerization with vinyl halides to give improved resistance to light. However, it is generally incompatible with useful solvents and polymer surfaces.
A further method for obtaining improved properties is suggested in U.S. Ser. No. 234,995, filed March 15, 1972, now U.S. Patent 3,859,330, wherein a copolymer of tetrafluoroethylene with a vinyl ether containing an ultraviolet-absorbing moiety is employed to give light-resistant coatings.
It is also known that polycarbonate or acrylate surfaces can be improved by the use of 2-hydroxy-4-methoxybenzophenone with mixtures of aliphatic and aromatic silanes as shown by U.S. Pat. No. 3,451,838. However, further improvements in abrasion resistance, compatibility, availability, stability and ease of application are desired.